Objectives for taking, printing, and projecting lenticular films



Dec. 3, 1935 K. RNTscH OBJECTIVES FOR TAKING, PRINTING AND PROJECTING LENTICULAR FILMS- Filed June 15, 1934 c B y R l/ Patented Dec. 3, 1935 OBJECTIVES FOR TAKING, PRNTING, AND

PROJECTING LENTICULAR FILMS Kurt Rntsch, Teltow-Seehof, near Berlin, Germany, assigner to Opticolor, Aktiengesellschaft, Glarus, Switzerland.. a corporation of Switzerland Application June 15, 1934, Serial No. 730,715 In Germany June 22, 1933 7 Claims.

The invention relates to objectives for taking, printing and projecting lenticular iilms and more yparticularly to such objectives which are associated with a multicolor screen or are provided with a diaphragm which to a certain degree has the eiiect of a polychromatic screen.

If the image of the multicolor screen or'of the diaphragm seen from the lm appears distorted, color dominants will be caused. The distortion is especially great with such di-aphragms or screens which are mounted in the interior of the objective, this beingv corrected as a whole, its single parts having no or an insufficient correction.

Ii the multicolor screen and the adherent diaphragm are mounted in the interior of the objective, the bands of the screen are seen in another greatness from the middle of the picture field but from a point lying at the margin of the picture field. A band at the margin of the screen e. g. being seen comparatively greater from the margin of the picture iield than a middle band, this lateral band will predominate in its color towards the margin of the taken or printed or projected picture. Quite the contrary results, if a lateral band is seen from the margin of the picture field comparatively smaller than a middle band.

These dominants may be avoided by the known v'means providing a diaphragm remote from the screen, which is only eiiective for such parts of stronger if diaphragm and multicolor screen are separated. With'such objectives the filter consists of a great number of bands, the colors of which periodically repeat. A multicolor screen with the three elementary colorsred, green and blue being taken as basisthe three middle bands may be continued by two other bands also with the colors red, green or blue on vevery side of the screen, the colors recurring cyclicly over the whole lter. The diaphragm should be shaped in this case in such a manner, that the ratio of the areas of different color seen from different points of the picture field is constant. The diaphragm eg. may have a'rectang'ular shape and may be chosen Aso wide, that the three middle bands of the color illter are to be seenlfrom the middle of the picture field. Four diiierent bands are generally seen from the points lying beyond the middle of the picture iield, two bands havlng-the same color. These bands shall supplement one another in the amount of their whole area in such a manner, that color falsiiications do not arise. Other shapes of diaphragms, for instance a hexagon, may be applied instead of the rectangular diaphragm.

It is a condition which is to be observed with 5 objectives the diaphragm of which is separated from the lter, that the bands of the same color shall have the same width, eventually inclusive of opaque intervening spaces. In this case the color iilter is often mounted in front of the ob- 10 jective, for instance in the front focal plane, the diaphragm being mounted in the interior of the objective.

For a fuller explanation of the invention, its

objects and advantages reference will be made l5 to the accompanying drawing wherein the same reference characters denote the same parts throughout and in which:

Fig. l is a diagram-illustrative of they principle of the optical systems comprising an objective, a 2o diaphragm and a screen, the screen being distant from the diaphragm;

Fig. 2 shows a sectional side view of such an optical system; y

Figs. 3 and 4 are illustrative of the defect, 25 which is to be observed with the existing objectives making them inappropriate for use with lenticular lms; 4

Figs. 5-10 are diagrams of different color screens embodying the invention. 30

In Fig. l the film is situated at I. The image of the diaphragm seen from the film (the pupil of emergence of the objective) is indicated by 2, the image of the screen seen from the iilm being placed at 3. in the iinite. However, the following considerations are exactly the same, if the image of the screen is placed in the infinity. From the point 4 lying in the middle of the iilm gate the three middle bands G, R, B of the iilter 3 will be seen 40 through the pupil 2, which for` instance may have a rectangular shape. From a point 5 on the margin of. the lm gate instead of the band B the band B1 of the same color-is visible and of the band R only apart, but therefore the band R1 45 will be seen. If` for instance a hexagonal diaphragm is used instead of the rectangular diaphragm, the bands G and B are to be seen from the point 4 cut in the height in diagonal direction and therefore edges Aoi.' the bands B1 and G1 are visible.

In Fig. 2 an objective is represented, the pupil and the image of the screen having the same position as in Fig. l. The objective .6 in the interior contains the diaphragm 1, which is to be seen 55 The image of the screen is situated 35 mined bythe bands B1or G1. a change of the ydifferent predominating colors results in advancing in lateral direction over the l color bands) from the film at the place 2. Before the objective there is situated a color screen 8, which seen from the iilm seems to be placed at 3.

Hitherto the wide of the filter bands and the aperture and shape of the pupil 2 were only chosen accordingy the method illustrated `in Fig. 1.

This method however is not sufficient, and defective objectives are produced'. The diaphragm "1 being placed in the interior oi the objective and for instance having a rectangular shape, it is not seen from the film 2 as rectangular but Aas a quadrangle with crooked lines. In Fig. 3 the bands R1, B1, G, R, B, G1, R: are shown in a front view. The color screen being seen in this example through the whole objective, these bands appear wholly 'or at least approximately undistorted. From the point 4 of the hlml gate that part of the color screenvis visible, which consists of the quadrangle 9 with'crooked lines. `It is evident, that the whole visible area of the bands G and B is little greater than the visible area of the band R. Beyond thislittle parts of the bands-B1 and G1 are to be seen. Looking through theobjective from a. point out of the optical axis for instance point 5, that part of the color is visible, which is represented by the quadrangle I0. 'I'his quadrangle is distorted in quite another way than the quadrangle 9. Thus, the band G1 is Vseen greater than forinstance the band B, and the whole area visible of the bands R and Rz is still .gate; However, for an interiacent point of the picture eld, from which the bandsRi or R2 on the margin ofthe color screen are not yet to be seen, the colors predominate, which are deter- It is evident, that picture held. Y

The manner in which this change proceeds is to be understood from Fig. 4. In this gure the abscisses represent the distances of the points of the lm gate from the perpendicular through the middle of the gate (parallel to the direction of the trate which parts of the areas of the color screen are to be seen from'the points of the film gate. The portions ot red, green and blue light effective for the middle of the lm gate are subtracted, the curves'only representing the difference from the .i proportion of the bands'of different colors in the middle of the iilm gate. The meaning of the curves is as follows: vAdvancing from the middle of the lm gate towards the margin, for instance to the point l I, the equal area 'of the bands of the colors determined by G and R is seen as from the middle of the lm gate.

However a much greater part of the area of. the color indicated by B is to be seen, and the difference from the middle of the illm gate amounts to' nearly 5% at point Il. In agreater distance from the middle of the gate the vsurplus portion of the color determined by B continually increases and reaches nearly 10% nally diminishing again.

'Ihere a predominating of thefcolor determined by R ls to -be observed, as it is shown by Fig. 3. The

bands of the color determined by R will be seen.,

' on the margin with a much greater area than from the middle. 1

There are the same proportions in advancing from the middle of the lm gate towards the The three curves r, g, and b illus`y otherside. At rst the color determined by G is predominating, and on the margin the color of the band R1 predominates again.

- 'I'he defects arising with the screens ,known hitherto were explained above by the example of 5 an objective, comprising a color screen, which consists of seven different bands.l The defects are the same, if. the screen consists of more or less differently colored bands. If the distortion of the pupil seen from the lm is not cushion-like as illustrated in Fig. 3, but if it is barrel-shaped, the preceding facts are also unchanged in principle.

For removing the defects described above diaphragms or diaphragming means are used. These are preferably arranged immediately on the color screen. Fig. v5 representsva front view of the means which, though'not wholly removing the defects, considerably reduce them. The opaque strips of the color screen represented in 20 Fig. 5 being arranged between the single bands of the color screen, have a different width. 'I'hey are comparatively narrow between the bands G, R, and B and only of such a width, that the undesirable diiusion between the parts' of the 25 photographic layer appertaining to the different bands of the screen is reduced to a tolerable degree. However, the strips between the bands on the margin of the screen have a much greater width, the curves 1', g, and b represented in Fig. 4 80 thereby being leveled down. 'I'he course of these curves is influenced in such a manner, vthat they are partly positive and partly negative and run closely to the abscisse axis.

Another means which removes the dominants 85 with greater success is represented in Fig. 6.'

, Thisgure sho-ws a sectional view. of a color screen consisting of seven bands. Grey-wedges K1 to K4 are laid on the bands R1, B1, G1, and R2.

y The course of the characteristic curves of those 40 screens which should be made according to the in a sectional view. For the sake of an easier manufacture the grey-wedges K2 and K3 of Fig. 6 are replaced by two grey-screens L2 land La in y form of steps.

Moreover grey-screens L1 and Li are arranged l on the bands R1 and R2. y The whole is covered 60 *I with a layer S of transparent materialto obtain an exact paralellism of the faces of the screen.

The same effect which is obtained with the y screens represented in Figs. 6 and '7 should be reached to a certain degree by giving a greater transparency to the bands on which the greyivedges are arranged. Instead' of the grey screens diaphragms according to Figs. 8 and 9 may be used. 'I'hese gures show front views of color filters embodying 7 the invention. The bands R1, B1, G1, and Rz of Fig. 8 are covered with tapering diaphragms M1 toM4. These should be made of an opaque material, for instance cut out of black paper and the like and pasted on the bands. They are arvranged on the bands in middle height for being also visible and effective for the points on the upper and the lower margin of the lmgate. Sometimes it should be advantageous to provide on the screen not only one but several of the tapered masks. Such a filterconssting of six bands is shown in Fig. 9. Tapered diaphragms M1 to M4 and M1 to M4 are arranged two by two on the bands R1, B1, G1 and R2. To show in which circuit the masks have to be arranged on the bands, the part of the screen is represented Which is visible from a point in the corner C-f the lm gate. The diaphragms should be arranged in such a manner that they are visible from all points.

Instead of the masks represented in Fig. 9 a great number of very thin and tapered diaphragms should be used and vshould be arranged at the same distances over the length of the bands to be covered. If the number of the masks is great enough, the eifect is similar that of a grey-wedge laid on, and no defect arises if from each point of the lm gate only a part of the masks of each band is visible.

With the examples described above it has been suggested, that the distortion o'f the diaphragm seen from the nlm-gate is cushion-like. If the distortion is barrel-shaped, the defects produced by it should be eliminated. by arranging the diaphragms not on the bands on the edge but on Athe middle of the screen.

Such a color screen, the middle bands of which are diaphragmed, is shown in a front view in Fig. 10.A

The bands G, R, and B are covered ,in the middle by the masks M5, M6, and M7. Instead of these masks the other means represented in Figs. 5. to 9 may be applied.

The scope of the invention has been illustrated above for such optical systems, with which a color screen consisting of one or more bands is associated with the objective. However, the invention also comprises optical systems used in copying, a diaphragm being arranged at the place of the color screen. This diaphragm may be used for copying with diiferent intensity the colors belonging to the different bands. In this case the diameter of the aperture of the diaphragm should not be chosen only proportionally to the quantities of light which are to be used in copying, but it has to be taken into account that the shape -of the aperture is changed by the distortion.

I claim as my invention: 1. An optical system for use with lenticulated lms comprising an objective-and a diaphragm,

a color filter spaced from' the diaphragm andl comprising recurrent series ofzones of different color valuesfthe sum of the valuesl in any oneA series `giving substantially the effect of white light, and masking means applied to certain of said zones, the amount of masking effected on the various zones progressively changing from and comprising recurrent series of zones of different color values, the sum of the values in any one series giving substantially the effect of white light, and masking means applied to certain of said zones, said masking means being so arranged and constituted that the product obtained by multiplying the area of any zone by its transparency is constant, as viewed from different points on the lm used with the objective.

3. An optical system for use with Ienticulated lms comprisingA an objective and a diaphragm, a color lter spaced from the diaphragm and comprising recurrent series of zones of different color values, the sum of the values in any one series giving substantially the effect of white light, and masking means applied to certain of said zones, the amount of masking effected on the various zones progressively increasing from the center of the filter towards the edge zones.

4. An optical system for use with lenticulated lms comprising an objective and a diaphragm, a color lter spaced from the diaphragm and comprising recurrent series of zones of different color values, the sum of the values in any one series giving substantially the effect of white light, and masking means applied to certain of said zones and comprising wedge-shaped diaphragms varying in width transversely of said zones and applied to the zones which appear to be too great because of the distortion of the objective.

5. An optical system for use with lenticulated lrns comprising an objective and a diaphragm,

a color illter spaced from the diaphragm and films comprising an objective and a diaphragm,

a color,- lter spaced from the diaphragm and A comprising recurrent series of zones of different color values, the sum of the values in any one series giving substantially the effect of white light, and masking means applied to certain of said zonesy and comprising Wedge-shaped diaphragms varying in width and'in opacity transy versely of said zones and applied to the zones which appear to be too great because ofthe distortion of the objective.

7. An optical system for use with lenticulated films comprising an objective and a diaphragm, a color lter spaced from the diaphragm and comprising recurrent series of zones of different color values, the sum of the values in any one series giving substantially the eifect of white light, and masking means applied to certain of said zones and comprisingv a plurality of diaphragms applied to one or more of said zones and extending transversely thereof.

' KURT RNTSCH. 

